The present invention relates to harvesting machines. More particularly, the invention is directed to combines for mechanized harvesting of sugar cane in an efficient and economical manner.
The prior art has disclosed automated machines for the harvesting of sugar cane which include apparatus employing means for following the ground relief; cutting of frontal and lateral stalks; feeder-crosscutter for the cut cane; and impurity transporting and separating assemblies mounted on the chassis. It is also known to employ equipment which utilizes a chamber for pneumatic separation, with two conveyors arranged in cascade, where the upper one is situated under a suction duct and a lower one is located in the air flow zone of a propelling conduit for directing air current from a blower toward the chopped mass. Also known are pneumatic separation chambers which comprise a conveyor to deliver chopped stems and a propelling duct located under the conveyor. To decrease the whirling and harmful air currents, the chamber at the end zone of the conveyor is equipped with a perforated top.
Also known are crosscutting devices which divide the cut cane into chunks of a given length, which employ two pair of radial blades diametrically opposed with respect to each pair, which rotate in an opposite direction and toward the encountering mass. The blades coincide twice during each revolutions, thus crosscutting the mass of cane passing between them (see U.S. Pat. No. 3,599,404 and No. 3,659,404). There also is known crosscutting devices with blades arranged tangentially on drums, in order to increase cutting capacity.
Supporting shoes or runners for the harvesting section are disclosed in U.S. Pat. No. 3,599,404, which is used to limit the height at which the cutting device makes the lower cut.
Other cane combines known utilize the system of microrelief copying, crosscutting of the stems and the other conventional harvesting elements, but which differ from the previous ones, as regard the arrangement used in the separation of foreign matter. The cleaning chamber of these combines includes a conveyor comprising three drums transverse to the chamber which conducts the crosscut vegetable means toward a zone where a flow of air produced by an extracting blower. The blower is located with its axis of rotation perpendicular to a horizontal plane of the chamber and practically over thd drums. In turn, the lighter mass is sucked up and ejected through the body of an extractor.
Also known are devices to control the air flow which intercepts the flow and includes a guide element comprising a plurality of vanes of arcuate shape to eliminate that part of the component which produces the rotational movement of the flow provoked by the blower. In another known device, a rotating element has been incorporated over the blower, coaxially to the blower, pervious to the passing of the air and impervious to the passing of foreign matter, which, when contacted, are deflected to the hoppers, directed downwards and located at each side of the body of the blower. In another known apparatus, the vanes used to decrease the rotating movement of the air flow are located at the suction side of the blower. A looped conduit located around the upper part of the body of the blower is employed, where the walls define an annular opening to receive the foreign matter ejected by the blower, under the action of a centrifugal force.
It also has been noted, that in placing cleaning chambers by extraction on top of the unloading conveyors of some of the chambers, the axis of rotation of the blower has been slightly slanted, thus producing an almost vertical suction.
In regard to prior art cleaning chambers, there are great power consumption demands due to the large field of action of the propelling flows and the need to control proper air flow when separation of foreign matter is accomplished, throughout the length of the chamber. Furthermore, it is very difficult to stabilize the working rate of the blowers because the speed of the air needed to eject part of the foreign matter is very close to the speed needed for the pneumatic transportation of the cane chunks, which results in heavy losses of cane during the cleaning process. Another defect to these machines is that the pneumatic separation is accomplished with only one blower provoking a large hydraulic resistance and decreasing the outflow of air, which affects the quality of the cleaning. Also the possibility of obstructing the blower with consequent damage to the rotor exists.
Due to the recirculation of air producted by prior art blowers, there is a limitation in the pneumatic separation in suction flows; in part, due to the need for structure to prevent the sucked foreign matter from reaching the rotor, thus partially interfering with the air intake of the blower. Furthermore, in order to direct the propelling flow of the blower to zones where the other cleaning points are located conduits must be used, the shapes and lengths of which provoke high energy losses of the air flow. As a consequence of all this, there is the need of intensifying the volume of the flow of air. Pneumatic separation is accomplished when the air is directed to a chopped mass, however, the composition and quantity of the mass can adversely affect this with the result that it becomes difficult to stabilize air flow for the different working conditions of the harvester.
Other machines have tried to overcome the aforementioned difficulties by decreasing the dimensions of the pneumatic separation chamber and its power consumption without achieving a satisfactory result. Further disadvantages which still persist include: a reduced working capacity due to the vertical location in the chamber; the action time of the suction air flow produced by the blower over the vegetable mass is insufficient; the sudden change in the path of the foreign matter travel decrease productivity and limits its utilization in high yielding fields.
Another drawback of these cleaning chambers is the high hydraulic resistance, that is, the existence of static pressures due to chamber configuration. As a result, there is a loss of energy in dynamic pressures, that is, in velocity of the air current. This translates negatively in the efficiency of the blower, which is already affected, as regards the consumption of current. Furthermore, the prior art chambers, because of the restriction of the air flow require the introduction of movable elements, in order to guarantee the entrance of the air.
A problem which has not been resolved satisfactorily is the control of the trajectory of the foreign matter ejected by the blower in order to prevent them from falling on top of the canes which have not been harvested or on top of the transportation means which receives the clean cane for transportation to the factory. The known solutions resolve only part of the problem in some cases, by employing complex construction which however, can provoke obstruction of the blowers.
Other deficiencies which have been detected in connection with these prior art harvesting machines are that the cleaning is very sensitive to the degree of cutting of the vegetable mass harvested. During the utilization of the equipment, the crosscutting blades are worn out very rapidly and the minimum of clearances between the sharp edges of these elements reduces crosscutting effectiveness and in turn a loss of suitable cleaning. Known crosscutters, such as disclosed in U.S. Pat. Nos. 3,599,404 and 3,659,404 require constant regulation of the clearance between the sharp edges of the blades and the frequent changing of the blades. These machines are characterized also by the lack of efficiency of the copying devices of the microrelief, which, without suitable regulation of the height of the cut, necessitate very complex and robust structures for the copying members, see U.S. Pat. No. 3,599,404.